In the games

Giovanni is the primary antagonist of the games taking place in Kanto.

In the first games Giovanni appeared in, he served a dual role: one that was well-known to the residents of Kanto, and one that was more secret. He was first shown as the leader of the villainous Team Rocket, the first of many criminal organizations to grace the Pokémon games. After he and his team of Grunts were defeated at Silph Co. by an eleven-year-old boy, Giovanni fled to a hideout that his antagonist was unaware of. Once the player returned to Viridian City, one of the major plot twists of these games revealed that Giovanni, in addition to his role as a criminal, was the final Gym Leader to be fought before the Elite Four—albeit one without a formal title. Here, he specializes in the Ground type. Once defeated, he disbanded Team Rocket and left the player with the Earth Badge and TM27 (Fissure). He then vanishes, and is not seen again.

Giovanni's role in Pokémon FireRed and LeafGreen is much the same; the one difference is that defeating him in the Gym battle will earn the player TM26 (Earthquake), instead of TM27 (Fissure). He also implies that he intends to return to power one day rather than being moved to dedicate his life to the study of Pokémon. There is a side-plot in the Sevii Islands that revolves around Giovanni; a group of Team Rocket members are trying to continue the aims of Team Rocket, but they abandon this when they realize that their leader has been defeated once and for all.

In Pokémon Gold, Silver, Crystal, HeartGold, and SoulSilver, a group of Team Rocket members tries to relaunch the old team. They take over Goldenrod Radio Tower, and broadcast a radio announcement intended for Giovanni. Only in HeartGold and SoulSilver is it revealed that Giovanni does hear the broadcast, from his hideout in Tohjo Falls - an event in the remakes involving a time-traveling Celebi allows Ethan and Lyra to travel back in time and defeat Giovanni at the same time the rest of Team Rocket is being defeated. Like before, once defeated, Giovanni will disappear. Later, in Kanto, it is revealed that Blue took over the Viridian Gym after his disappearance.

The Celebi event also reveals some of Giovanni's background from the three years between Generation I/III and Generation II/IV. While it was mentioned in FireRed and LeafGreen that Giovanni has a son with red hair, the son's identity wasn't revealed until the time-travel event in HeartGold and SoulSilver. As many fans speculated (and as was mentioned in the Pokémon Adventures manga series), this son is the rival of the Johto player character, Silver. Much of Silver's personality is a result of the treatment he received from Giovanni, which includes abandonment. Like many of Giovanni's other actions throughout the games, this reflects on his selfishness.

Giovanni reappears in Black 2 and White 2 in the Pokémon World Tournament, replacing Blue, who instead participates in the Champions Tournament. Giovanni returns to using Ground types exclusively. While the announcer usually introduces Gym Leaders by their title, Giovanni, who does not have a title, is introduced as "The Self-Proclaimed Strongest Trainer" (Japanese: さいきょうの トレーナーと なのるClaiming Himself the Strongest Trainer).

"Fwahahaha! This is my hideout! I planned to resurrect Team Rocket here! But, you have caught me again! So be it! This time, I'm not holding back! Once more, you shall face Giovanni, the greatest trainer!"

Being defeated

"Ha! That was a truly intense fight! You have won! As proof, here is the Earth Badge!"

After being defeated

"The Earth Badge makes Pokémon of any level obey! It is evidence of your mastery as a Pokémon trainer! With it, you can enter the Pokémon League! It is my gift for your Pokémon League challenge!"

"TM27 is Fissure! It will take out Pokémon with just one hit! I made it when I ran the Gym here, too long ago..."

"Having lost, I cannot face my underlings! Team Rocket is finished forever! I will dedicate my life to the study of Pokémon! Let us meet again some day! Farewell!"

"So! I must say, I am impressed you got here. Team Rocket captures Pokémon from around the world. They're important tools for keeping our criminal enterprise going. I am the leader, Giovanni! For your insolence, you will feel a world of pain!"

Being defeated

"WHAT! This can't be!"

After being defeated

"I see that you raise Pokémon with utmost care. A child like you would never understand what I hope to achieve. I shall step aside this time! I hope we met again..."

"Fwahahaha! Welcome to my hideout! It shall be so until I can restore Team Rocket to its former glory. But, you have found me again. So be it. This time, I'm not holding back! Once more, you shall face Giovanni, the greatest Trainer!"

Being defeated

"Ha! That was a truly intense fight. You have won! As proof, here is the Earth Badge!"

After being defeated

"The Earth Badge makes Pokémon of any level obey without question. It is evidence of your mastery as a Pokémon Trainer. With it, you can challenge the Pokémon League. Also, take this TM. Consider it a gift for your Pokémon League challenge."

"TM26 contains Earthquake. It is a powerful attack that causes a massive tremor. I made it when I ran the Gym here, far too long ago..."

"Having lost in this fashion, I can't face my followers. I have betrayed their trust. As of today, Team Rocket is finished forever! As for myself, I shall dedicate my life to training again. Let us meet again someday! Farewell!"

".................. One must acknowledge one's defeat before he can move on... I will go solo...for now... So that one day I will form a stronger organization!"

"Putting together the potential of many is how you produce a huge power... That's what an organization is... That's the strength of an organization! I failed...to make the best use of my subordinates' potential...! But you shall witness one day the revival of me and my Team Rocket!"

"My old associates need me... We will not repeat the failure of three years ago! Team Rocket will be born again, and I will rule the world!"

After sending out last Pokémon

"What in the world was that? Don't tell me some inexperienced kid can possibly be that strong!"

During battle, last Pokémon low on health

"What was that?"

Being defeated

"What in the world are you?"

After being defeated

"How this is possible...? The past three years have been a waste...? How can a kid like you manage to destroy my dream once again? The precious dream of Team Rocket has become little more than an illusion..."

If the player is defeated

"Mark my words. Not being able to measure your own strength shows that you are still but a child."

In the manga

In the Pokémon Adventures manga

In Pokémon Adventures, Giovanni serves much the same role as he does in the games, although he now has Lt. Surge, Sabrina, and Koga as subordinates. However, Giovanni is much more ruthless than his other counterparts.

In the Pokémon Pocket Monsters manga

In the Pokémon Zensho manga

Giovanni in Pokémon Zensho

Giovanni appears in Celadon City watching Satoshi from the hidden cameras within the Silph Co. building. He has one of his minions to try to stop Satoshi from reaching him. Two chapters later, he has taken the boss of Silph Co. hostage and threatens to harm him if he refuses to tell Giovanni where the Master Ball was. However, he is interrupted when Satoshi and Sabrina teleport their way to the top floor. Lapras uses Mist to blind Nidoqueen, but she launches a Poison Sting attack. One of the needles from the attacks hits Giovanni. Satoshi and the others manage to escape afterwards. In Viridian City, Giovanni was revealed to be the final Gym Leader that Satoshi challenges. Satoshi manages to defeat him and earns the Earth Badge.

Pokémon

Nidoqueen ♀

While taking over the Silph Co., Giovanni used Nidoqueen to hold the Silph co. boss hostage.

At the Pokémon Tower

Machamp

Giovanni has owned this Machamp ever since he was a child. When it passed away, it turned him into a bitter person. The spirit of Machamp was called out by one of the Team Rocket grunts to deal with Satoshi. However, it was defeated by Gastly as physical attacks had no effect on the Ghost-type Pokémon.

Giovanni has owned this Nidoking ever since his childhood. He first appeared in Satoshi's flashback while Satoshi was in his house. At the Viridian Gym, Nidoking appeared in Giovanni's imagination where it was revealed that his passing during Giovanni's childhood turned him into a bitter person.

Cards

Giovanni's PokémonCards listed with a blue background are only legal to use in the current Expanded format.Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.

Trivia

In the games, Giovanni is the only Gym Leader to appear outside of his Gym in Generation I, a feature that would become more and more common up to Generation IV, during and after which all Gym Leaders in the featured regions appear outside of their Gym in one way or another.

In the English version of Pokémon Stadium, his name is misspelled "Giovani" (with one n). This is because the space for Trainer names only allows seven characters, whilst Giovanni's name has eight.

Both Giovanni and Juan are the eighth Gym Leader in a region introduced in an odd-numbered generation. Both of their names are a foreign version of the name "John." Also, in Generation III, the manuals show them to be an unknown Gym Leader.

In the official Red and Blue guide from Nintendo Power, Giovanni was labeled to be a regional boss of Team Rocket (implying he's not the absolute leader). This was invalidated in Gold, Silver, and Crystal, where it was made clear that Giovanni was the absolute leader of Team Rocket (even having an office in Johto).

Giovanni was the first Gym Leader who can be battled more than once, and is still the only one who can be battled before the Gym battle.

This also makes him one of three Gym Leaders who does not give a Badge to the player immediately after the first defeat, the other two being Whitney and Clair.

He is the only Gym Leader to have two titles in the same game as being Gym Leader, the titles being "Boss" and "Gym Leader."

Giovanni's Nidoking and Rhydon, both being at level 55 during the Gym battle in Yellow, are the highest leveled Pokémon to be owned by a Gym Leader during the initial battle with them, tied with Marlon's Jellicent in Challenge Mode.

Giovanni is also the only criminal boss in the anime to have shown to have Pokémon of his own, not just controlled legendary Pokémon atsomepoint.

Giovanni is likely based on the boss of a Yakuza faction, possibly more on the bakuto factions than others, considering Team Rocket's former ownership of the Celadon Game Corner. Outside of Japan, this reference is localized, making him more akin to a Mafia boss (especially considering his English name being Italian in origin).

Giovanni and Blue are the only two Trainers to have three different battle themes. Both were the leader of Viridian Gym at one point.